I have had my road bike for 18 months. After a few months of purchase I bought a Decathlon chain measurement tool, used it regularly and was pretty good about cleaning and oiling the chain.
I am 186cm tall and weigh 70 kilos and ride perhaps 40-50 miles a week. I was quite surprised that my chain wear tool was telling me after about 10 months that I needed a new chain. I procrastinated for maybe a month, and then got my act together on Boxing Day last year. I could have replaced a little earlier, but I do not think I trashed the cassette.
So, the new chain (KMC 8-speed, £8 from Decathlon) has been on the bike for just over seven months now. My chain wear tool is showing that there is still room for the tool to drop i.e. it is not lying flat on the chain. Doing a 12-inch steel rule test today, however, suggests that I should think about replacing the chain, because the chain has lengthened by the width of a pin, which is 1/8 of an inch, Leonard Zinn in his Road Bike Maintenance book says that when the lengthening is 1/8 of an inch or more, the chain needs replacing.
So Decathlon's tool says I have a little more life in the chain, but a ruler test says I should replace it now. I guess I must have done in 7 months about 1250 miles on the chain.
Does this mileage seem a little low? Zinn says that a heavy rider might only get 1000-1500 miles from a chain, but a light rider who doesn't clean the chain could get 2-3000 miles or 5000 miles if he looks after the chain.
I look after the chain (oil regularly), and do not stand up on the peddles. I do a lot of gear changes according to terrain, traffic and when I am coming to a stop (easier to burn off from the lights in a higher gear).
At 70 kg am I a "heavy rider", or should I be buying more expensive chains? Or should I see an £8 chain as a 6-7 month consumable and put a new chain on well within the wear period to protect the cassette?